On 06/18/2017 09:01 PM, Charles Shih wrote: > Dear All, > > I'm reaching this mail-list to ask a small question about disabling > '3dnowprefetch' CPU feature in Xen Guest using libvirt. > > This is my environment: > Fedora release 26 (Twenty Six) > 4.11.0-0.rc3.git0.2.fc26.x86_64 > xen-4.8.1-2.fc26.x86_64 > libvirt-3.2.1-1.fc26.x86_64 > > I can disable '3dnowprefetch' CPU feature in guest via 'xl' command, > with adding `cpuid='host,3dnowprefetch=0'` into the CFG file. > > However, follow the instruction (https://libvirt.org/formatdom > ain.html#elementsCPU <https://libvirt.org/formatdomain.html#elementsCPU>), > I added the following block into my XML file: > > ``` > <cpu mode='host-passthrough' check='none'> > <feature policy='disable' name='3dnowprefetch'/> > </cpu> > ``` > > Created the instance, seemed this feature was not being disabled in > my guest. (I was able to see '3dnowprefetch' in `lscpu` outputs) > > Anybody has idea on this? Does libvirt support this for Xen? > Currently, the libvirt libxl driver only supports VMX or SVM CPU feature, and for that you'd need libvirt 3.3.0 http://libvirt.org/git/?p=libvirt.git;a=commit;h=c268b9eaeb4 321ef311ae2e152b80752918eb289 More support for CPU customization is on the todo list. Contributions are always warmly welcomed :-). Regards, Jim